In the month of March 1900, 2106 convicts and 719 contractors in the Ombilin mines, West Sumatra, produced 16417 tons of coal, according to the Javasche Courant.
More figures about Ombilin were presented in a contemporary publication: 'Forced labour is predominant. Although the number of free workers [= contractors] has grown over the past few years, in 1900 chain gangs performed 585,000 of the 827,000 shifts... In 1899 the desertion rate was extraordinary high, at times more than a hundred a month. The percentage of sickness and mortality was equally high.
Opium smoking, theft, murder, and pederasty are undeniable and difficult to counter. Theft is not as widespread as expected in a place full of criminals of the lowest kind. But the frequency of murder is much worse. In 1901 16 murder cases occurred in an average population of 2400 convicts.' (Uit Onze Koloniën pp 32-34)